High-entropy driven electronic and microstructural synergy for superior capacitive energy storage in lead-free ceramics

Abstract Dielectric capacitors, characterized by their high power density and ultrafast charge/discharge capabilities, are pivotal components in modern pulsed power and renewable energy systems. However, the widespread adoption of ferroelectric ceramics is inherently hampered by the antagonistic relationship between polarization (P) and breakdown strength (Eb), further compounded by significant polarization hysteresis and losses, which collectively obstruct the simultaneous realization of high recoverable energy density (Wrec) and efficiency (η). Herein, we transcend this fundamental limitation via a novel high-entropy engineering strategy in (Bi, Na)TiO₃-based ceramics. The designed materials achieve an exceptional Wrec of 11.1 J/cm³ and a remarkably high η of ~ 89.1%. This breakthrough is attributed to a synergistic interplay of mechanisms orchestrated by the high-entropy design: (i) a reduction in electronic band curvature that increases the charge carrier effective mass, thereby suppressing mobility and electrical conductivity; (ii) the emergence of self-assembled core-shell microstructures that effectively impede electrical treeing propagation through interfacial stress buffering and field homogenization; and (iii) the stabilization of nanoscale rhombohedral-orthorhombic-tetragonal-cubic (R-O-T-C) multiphase coexistence, which enhances dipole reorientability and disrupts long-range ferroelectric order. The confluence of these effects culminates in a significantly enhanced Eb while maximizing the polarization disparity (ΔP = Pmax ​- Pr). This study establishes high-entropy engineering as a transformative paradigm for designing advanced lead-free dielectric capacitors with superior energy storage performance.